Drum rotor

ABSTRACT

DRUM ROTOR HAVING A ROTATION-SYMMETRICAL, PREFERABLY CYLINDRICAL MANTLE AND AT LEAST ONE END WALL ATTACHED THERETO AND BEING ADAPTED TO BE ROTATED ABOUT ITS AXIS. THE MATERIAL IN THE END WALL HAS A RATIO BETWEEN DENSITY AND MODULE OF ELASTICITY WHICH IS SO MUCH HIGHER THAN THE CORRESPONDING RATIO FOR THE MANTLE THAT THE ELONGATIONS IN THE MANTLE AND THE END WALL IN THE JUNCTURE THEREBETWEEN DUE TO THE CENTRIFUGAL FORCE ARE ESSENTIALLY EQUAL.

Sept. 28, 1971 G. w. BRANDT DRUM ROTOR Filed June 17, 1968 United StatesPatent 3,608,395 DRUM ROTOR Gunnar Walter Brandt, Nykoping, Sweden,assignor to Aktiebolaget Atomenergi, Stockholm, Sweden Filed June 17,1968, Ser. No. 737,731 Claims priority, applic9atio1 Sweden, June 28,1967,

Int. Cl. F16f 15/30; B04b 7/00 US. Cl. 74-572 4 Claims ABSTRACT OF THEDISCLOSURE The present invention relates to a drum rotor for use forinstance in centrifugation at a high speed of rotation.

In conventional designs of drum rotors adapted for a high speed ofrotation consisting of a cylindrical mantle and end walls attachedthereto the structure, during the rotation of the drum, is subjected toforces in radial direction tending to stretch material in mantle and endwalls. By experience and calculations it can be shown that theelongation in the mantle is greater than the elongation at the outeredge of the end walls. From this reason unacceptable additional strainarises at the juncture between mantle and end walls, and this additionalstrain causes fiexural stress at the ends of the mantle. Thus, thematerial of the drum may be subjected to too high a strain with regardto its strength, besides which great difliculties arise in connectionwith the attachment of the end walls to the mantle.

The present invention has for a purpose to eliminate the problemsindicated above in drum rotors. The drum rotor according to the presentinvention has a rotation-symmetrical, preferably cylindrical mantle andat least one end wall attached thereto. The drum rotor is characterizedin that the material in the end wall has a ratio between density andmodule of elasticity which is so much higher than the correspondingratio for the mantle that the elongations in the mantle and the end wallin the juncture therebetween due to the centrifugal force areessentially equal.

The drum rotor is suitably made of a fibre-reinforced plastic, thematerial of the end wall having a smaller portion of reinforcing fibresthan the material of the mantle. Alternatively, reinforcing fibres maybe used in the end wall which have a lower module of elasticity thanthose of the mantle.

In a particularly preferred embodiment of the drum rotor of theinvention the portion of reinforcing fibres oriented in the direction ofthe main stress is lower in the material of the end wall than in that ofthe mantle. It is also possible to use a plastic in the material of theend wall having a greater density than plastic in the material of themantle.

The invention will now be described by an exemplifying embodiment withreference to the appended drawing that diagrammatically shows acentrifuge in section.

The centrifuge shown in the drawing is adapted for the separation ofgases having different molecular weights. The centrifuge includes a drumrotor having a cylindrical mantle 3 and an end wall 1, 2 attached toeach end of said mantle. An inlet tube for the gas mixture to be cenicetrifuged is connected to the end Wall 1, and said inlet tube 5 isconnected to the end wall 11 by means of a flange 6 in a manner notshown in detail, for instance by a weld or by screws. The end wall 1 isprovided with a central opening, through which connection with theinterior of the drum rotor is maintained through the inlet tube 5.

At a distance inside the end wall 1 and parallel thereto a partitionwall 15 is arranged which is provided with a series of inner apertures16 and a series of outer apertures 17, which apertures are suitablyarranged along concentric circles.

At the opposite end of the centrifuge a coupling assembly 8, 9 isarranged on the end wall 2, the rotatable coupling half 8 of which isattached to the end wall 2 by means of a flange 7. The fixed couplinghalf 9 supports a side outlet tube 11. Inside the end wall 2 andparallel thereto a partition wall 19 is arranged, which, as is the casewith the partition wall 15, is provided with inner apertures 20 andouter apertures 21, said apertures also being suitably arranged alongconcentric circles. On the lower surface of the partition wall 19 andoutside the inner apertures 20 a collecting cap 23 is arranged which atthe bottom end is connected to an outlet tube 12 provided at its innerend with a flange 25 for the connection to the collecting cap 23. Theinterior of said cap 23 is connected to the interior of the outlet tube12 through a central opening 26. The outlet tube 12 extends through thecoupling assembly 8, 9 and is rotatable relative the coupling half 9 andalso gastightly sealed thereagainst. The inlet tube 5 and the outlettube .12 are journalled in bearings not shown to allow the rotation ofthe rotor and thus act as pivots.

The function of the above described centrifuge is briefly the following.The drum rotor of the centrifuge is brought into rotation with a desiredspeed and the gas mixture to be separated is continuously supplied fromabove through the inlet tube 5. In view of the centrifugal force theheavy fraction of the gas mixture will be thrown outwardly towards thewalls of the mantle 3 and flows downwardly through apertures 17 as shownwith arrows in the drawing and further downwardly through the apertures21 in the lower partition wall 19. The heavy fraction then enters thespace between the coupling assembly 8, 9 and the outlet tube 12 and isdischarged through the side outlet tube 11. The light fraction remainsin the central parts of the centrifuge and flows downwardly through theapertures 16 in the upper partition wall 15 and further downwardlythrough the apertures 20 in the lower partition wall 19 and into thecollecting cap 23, from which the light frac tion leaves the centrifugethrough the outlet tube 12.

In the following it is assumed that the rotor works with a gas having alow pressure, for instance mm. Hg, in view of which the centrifugalforces acting on the gas are negligible as compared to the centrifugalforces acting on the mantle in view of the fact that the mass of the gasis much lower than that of the mantle.

Now assume that the mantle 3 and the end walls 1, 2 are made of the samematerial, viz. glass fibre-reinforced plastic. In the following Table Icertain data for the material of the drum rotor are given.

l Unsaturated chlorinated polyester, styrene modified Soredur G 10 1ncured form.

The mantle is assumed to have a diameter of 20 cm. and a length of 100cm. If the drum rotor is brought to rotate with a speed of 650revolutions per second it is possible to calculate from the data ofTable I that the radial elongation of the mantle is about 0.7 mm.,whereas the radial elongation of the end walls is merely 0.16 mm. Due tothis difference in radial elongation undesirable stress arises in thejuncture between mantle and end Walls.

While using the same material in the mantle the end walls are now madeof another material and in Table II below the corresponding data asthose of Table I are given for this material.

2 Polyvinylidene bromide in crystalline form.

It is possible from the data given in Table H to calculate that in thiscase the end walls will be subjected to a radial elongation of about 0.7mm., i.e. the same elongation as that to which the mantle is subjected.

It will be easily understood by those skilled in the art ,whatextraordinary advantages are obtained when mantle and end walls aresubjected to an equal radial elongation when rotated. Firstly, thematerial in the juncture between mantle and end walls is not subjectedto additional stress difficult to calculate, and, secondly, the joiningof the end walls and mantle need not cause any problems because therequirements as to the strength of the joint will not be high.

It is easily understood that the desired ratio between density andmodule of elasticity in the material in the end walls can be obtained inmany ways. The density of the material of the end walls can be increasedby selecting a plastic material and/or a reinforcing material having ahigh density. The module of elasticity can be lowered by lowering theportion of reinforcing fibres in the material 'of the end walls.Moreover, the module of elasticity can be essentially reduced byorienting the reinforcing fibres in the end walls essentially in anotherdirection than the radial direction which is a direction of the mainstress.

As a principle, any material may be used in the drum rotor of theinvention provided that the material fulfils the requirements as tostrength with regard to rotational speed, dimensions etc. However,thermosetting resins in combination with glass fibre reinforcement areparticularly suitable.

The mantle may also be reinforced with another fibre material than glassfibres, for instance with graphite fibres, the ratio between module ofelasticity and density of which is essentially higher than thecorresponding ratio for glass fibres, thereby causing a correspondingsmaller elongation in the mantle. It has surprisingly been found that itis possible to produce graphite fibres having a very high strength, thegraphite fibres being polycrystalline and consisting of small graphitecrystallites, the graphite planes of which are mainly orientedparallelto the fibre axis. The control of this orientation is essential toobtain a high strength. Further examples of reinforcing materials havinga high ratio between module 'of elasticity and density are found amongseveral groups of materials, for instance single crystals, so-calledwhiskers, polycrystalline materials, such as Al O ZrO and compositematerials, such as B 0 and SiC deposited on metal threads. The high.-strength of whiskers, that can consist of ceramic whiskers,

such as A1 0 and metal whiskers, for instance Cr, Cu, is supposed todepend on the fact that they have a high degree of crystallineperfection with few or no dislocations and that they are free fromsurface damages. For a cold-drawn metal thread having a small diameterthe strength is explained by the very strong-deformation and by acertain grain orientation.

It is also possible to use completely different materials in mantle andend walls, for instance lightweight metal in the mantle and glassfibre-reinforced plastic in the end walls. I w

The above considerations regarding the ratio between density and moduleof elasticity of the material of the end walls 1, 2 are, of course,applicable also on the partition walls 15, 19. The problems inconnection with said partition walls at the juncture between the mantleand these walls are exactly the same as for the end walls as regards theelongation during the rotation.

What is claimed is:

1. Drum rotor having a rotation-symmetrical, preferably cylindricalmantle made from a fibre-reinforced plastic and at least one end wall offibre reinforced plastic attached thereto and being adapted to berotated about its axis, the improvement wherein the material in the endwall has a ratio between density and module of elasticity which by meansof a difference in its reinforcing fibres in relation to the fibres inthe mantle is so much higher than the corresponding ratio for thematerial in the mantle that the elongations in the mantle and the endwall in the juncture therebetween due to the centrifugal force areessentially equal.

, 2. Drum rotor according to claim 1 made of fibre-reinforced plastic,characterized in that the material of the endwall has a smallerproportion of reinforcing fibres than the material of the mantle.

. 3. Drum rotor according to claim 1 made of fibre-reinforced plastic,characterized in that the material of the end wall has reinforcingfibres having a lower module of elasticity than those of the mantle.

4. Drum rotor according to claim 1, made of fibrereinforced plastic,characterized in that the proportion of reinforcing fibres oriented inthe direction of the main stress is lower in the material of the endwall than in the material of the mantle.

3/ 1958 Netherlands 233-27 FRED C. MATTERN, JR., Primary Examiner F. D.SHOEMAKER, Assistant Examiner U.S. C1.X.R.

